Eye surgery, or ophthalmic surgery, saves and improves the vision of tens of thousands of patients every year. However, given the sensitivity of vision to even small changes in the eye and the minute and delicate nature of many eye structures, ophthalmic surgery is difficult to perform and the reduction of even minor or uncommon surgical errors or modest improvements in accuracy of surgical techniques can make an enormous difference in the patient's vision after the surgery.
Ophthalmic surgery is performed on the eye and accessory visual structures. During ophthalmic surgery, a patient is placed on a support, facing upward. The support may a couch or a bed and may be positioned under a surgical microscope. An eye speculum is inserted to keep the eye exposed. Surgeons often use the surgical microscope to view the patient's eye, and surgical instruments may be introduced to perform any of a variety of different procedures. The surgical microscope provides imaging and optionally illumination of parts of the eye during the procedure.
In addition to simply allowing a close-up view of the eye, a surgical microscope may be equipped with an OCT system to provide additional information about internal structures of the eye that cannot effectively be seen using only the surgical microscope. OCT systems may be optically or electro-mechanically integrated into the surgical microscope.
OCT is an interferometric analysis technique for structural examination of a sample that is at least partially reflective to light, for example, a biological tissue. OCT can also be used for functional examination of a sample, such as the motion and velocity of the sample or blood flow in a tissue. OCT systems may be used to determine distance and depth profiles and other information based on interference patterns created by the interaction between a reflected beam from a reference mirror and a reflected beam from a sample.
In an OCT system, a single OCT source beam is split into two component beams, a sample beam that is propagated to and at least partially reflected by a sample, and a reference beam that is propagated to and reflected by a reference mirror. Each beam is typically reflected back to the beam splitter and combined, although certain OCT systems may not require each reflected beam to return to the beam splitter to be combined. When the reflected sample beam and reflected reference beam are combined, an interference pattern is generated, which may be used to measure distances and depth profiles of the sample and other information and to image internal target structures that the sample beam passed through. In ophthalmic surgery, an OCT system may be used, for example, to provide cross sectional views of the retina in high resolution.